1. Field of the Invention
The present invention relates to a vacuum cleaner, more particularly to a vacuum cleaner of an improved construction capable of simultaneously generating blowing and suction air streams so as to achieve a more thorough and effective removal of dirt and dust particles.
2. Description of the Related Art
Vacuum cleaners find wide applications be it in industry or in homes. Vacuum cleaners in general operate by suction to remove the contaminants, dirt or dust particles from an article to be cleaned. Vacuum cleaners of this type have to be maintained with a strong suction force and the suction mouthpiece thereof is normally placed in close contact with the surface of the article to be cleaned to effect removal of dirt and/or dust thereon. For articles having an uneven surface with convexities and concavities, such as electronic parts, carpets and woolen knitwear or materials, the suction mouthpiece of the vacuum cleaner is usually incapable of reaching the deeper and inner parts of such articles, and might even have difficulty in moving over the surface of the article to be cleaned. The mere suction function of the vacuum cleaner thus cannot be relied upon to effectively remove the contaminants, dirt or dust in the deepest part of such articles of uneven surfaces. In other words, only the surface dirt and dust on an article to be cleaned can be removed by such a vacuum cleaner, leaving behind the dirt and dust concealed in the deeper and inner part of the article. Thus, such a vacuum cleaner does not provide a thorough and fully effective cleaning.
In view of the drawback of such type of vacuum cleaners having a single suction function, those engaged in the related field consequently developed a vacuum cleaner designed to have both blowing and suction capabilities, which generally has a construction as shown in FIG. 1. The vacuum cleaner which is operable in the blowing or suction mode, as shown in the drawing, essentially comprises a tubular member 11 mounted on a main body 10. A switching valve 12 is disposed axially inside the tubular member 11. The switching valve 12 is rotatable and has two air passages 121 at one end thereof which are in fluid communication with the tubular member 11. A dust collecting pouch 13 is provided at the rear end of the main body 10. The lower end of the main body 10 may be connected to a source of air (such as an air compressor) via a tube (not shown). By pressing a handle 14, air is allowed to enter into the air passages 121 of the switching valve 12. When the air passages 121 of the switching valve 12 face toward the front of the tubular member 11 (see FIG. 1), the air is blown forward and outwardly from the front end of the tubular member 11 to form a blowing air stream, which is forced onto the article to be cleaned to stir and remove the surface dirt or dust. When the switching valve 12 is rotated so that the air passages 121 face the rear portion of the tubular member 11 (as best shown in FIG. 2), the air flows toward the inside to the rear end of the tubular member 11 into the dust collecting pouch 13 (see direction of arrow in FIG. 2), thus forming a suction air stream at the front end of the tubular member 11 for drawing in the dust on the surface of the article to be cleaned into the dust collecting pouch 13. The dual blowing and suction function for removing dirt or dust is thus achieved.
While the vacuum cleaner design described above has dual blowing and suction functions, some disadvantages in terms of its dust removing ability and ease of use are still noted. Specifically, this dual-function vacuum cleaner utilizes the switching valve 12 for changing the air flow direction in the tubular member 11 to achieve either a blowing or a suction effect. Therefore, such prior vacuum cleaners can only be switched to perform a single operation at a time, i.e., the on/off switch is used to change the air flow direction to switch the blowing function to suction function or vice-versa. In other words, the two operations of blowing and suction cannot be performed at the same time. Furthermore, the blowing and suction force of such a vacuum cleaner is insufficiently strong and, thus, the dust-removing effect is ultimately limited. In addition, when such vacuum cleaner is operated in the blowing mode for removing dirt or dust particles, the blowing air stream stirs up and scatters the dust around. The dusty surroundings caused thereby make breathing difficult and affects human health. Moreover, the scattered and flying dirt or dust particles will eventually settle on the ground so that the user must subsequently perform a cleaning/sweeping operation. Therefore, cleaning using such a vacuum cleaner is troublesome and time-consuming. Apart from the foregoing, when performing the suction operation, the front end opening of the tubular member 11 which serves as the suction mouthpiece must be adhered as closely as possible to the surface of the article to be cleaned for an effective suction of the dirt or dust particles. However, if the article to be cleaned has an uneven surface, or has elements thereon which can be easily broken upon contact (such as electronic circuit boards), the suction mouthpiece should not be placed too closely on the surface of the article to be cleaned and, naturally therefore, the cleaning operation is neither effective nor efficient.
The present invention is thus contrived in an attempt to alleviate the above shortcomings of the prior art.